1. Technical Field
The present invention relates to an illuminating device, and more particularly to a surface emitting type illuminating device suitable for a backlight of a liquid crystal display (LCD) or the like.
2. Related Art
In an LCD, a backlight unit is mounted on a back surface of the liquid crystal panel in order to perform transmitting display. In general, the backlight unit has a light source, a light guiding plate for irradiating lights from the light source onto the back surface of the liquid crystal panel as planar shaped lights, and a sheet for diffusing the lights emitted from the light guiding plate. The light incident onto the light guiding plate from the light source is repeatedly reflected between an exit plane and a reflecting plane of the light guiding plate, which is then emitted outward from the exiting plane.
Recently, dual display type cellular phones are being supplied to the consumer market. In a folding type cellular phone, a display unit (which corresponds to a cover in its structure) is foldably attached to a main body where operating buttons are mounted by means of hinge, and a large display panel is mounted on an inner side (which opposes to the operating buttons) of the display unit, and a small display panel is mounted on an outer side (the back side) of the display unit. That is, the large display panel and the small display panel are mounted in a back-to-back manner. Such an LCD is disclosed in Japanese Patent Laid-Open No. 2003-121655.
In the LCD disclosed in 2003-121655, one backlight unit is mounted in both large liquid crystal panel and small liquid crystal panel. However, a dual display type cellular phone which has two liquid crystal panels disposed in a back-to-back manner and one backlight unit interposed therebetween is also proposed. That is, one light emitting surface of one backlight unit is used for illuminating the large liquid crystal panel while the other light emitting surface is used for illuminating the small liquid crystal panel, so that reduced power consumption, a thin device, and a low manufacturing cost for the device itself can be realized.
In such a dual display type cellular phone, it is not necessary to light the two display panels at the same time, so that any one of the two display panels is typically lighted while the other is turned off. For example, in the above-mentioned cellular phone, when the display unit is opened so as to expose the operating buttons of the main body, a large display panel on an inner side of the display unit may be illuminated, and a small display panel on the outer side of the display unit may be illuminated only when the display unit is closed. However, one backlight unit shared by the two display panels generally emits light onto both panels.
Accordingly, the present invention has been made in consideration of the above-mentioned problems, and it is an object of the present invention to provide an illuminating device which is mounted on an electronic device such as a dual display type cellular phone and which is capable of saving power by illuminating only a necessary panel.